This proposal is submitted as part of the new Sustance Abuse Research. Grants program co-sponsored by NIAAA and NIDA. The purpose of the research proposed in this application is to conduct a series of studies derived from a theoretical framework of substance abuse and use based on the principles of social learning theory. The primary emphasis will be on the investigation of factors associated with the social etiology of both alcohol and marijuana use in a young adult population. Four types of studies are proposed: (1) Normative studies, to establish norms of alcohol and marijuana self-administration in a seminaturalistic setting (simulated bar and living-room environments), as a function of the following variables: sex of subject, presence or absence of others, and past history of drug use (high versus low risk for potential abuse); (2) Studies to determine the effects of manipulated social factors on the self administration of alcohol and marijuana, with an emphasis on the influence of peer models; (3) Studies to determine the effects of the administration of alcohol and/or marijuana on social behaviors, with an emphasis on interpersonal communication (including the expression of verbal aggression) in a male-female dyadic interaction; and (4) A study to assess the effects of marijuana on the subsequent self-administration of alcohol. The results of these investigations will have important implications for the development of both prevention and treatment programs in the problem areas of substance abuse and alcoholism.